The present invention relates to novel slug and snail baits, to a process for their preparation and to their use for controlling slugs and snails.
It is already known to control terrestrial slugs and snails using baits which comprise feedstuffs and molluscicidally active compounds, such as methiocarb, metaldehyde or metal chelates (cf. DE-A 35 03 608, DE 36 12 161 and WO 96-05 728).
Such slug and snail baits can be prepared, for example, by pressing one or more molluscicidally active compounds with feedstuff, carrier material, adhesives and other customary additives essentially dry into shaped articles. These baits have the disadvantage that they have a relatively rough surface, which causes undesirable abrasion during packaging, during transport and also during application. Moreover, it is unfavourable that these shaped articles are relatively unstable under the influence of rainwater, losing some of their activity owing to the beginning decomposition.
Furthermore, it is already known that slug and snail baits based on metaldehyde can be prepared by mixing the active component with the other constituents, but without adhesive, followed, after addition of water, by extrusion and processing into pellets. The activity of these shaped articles is good, but the physical properties under practice conditions are not always sufficient.
A slug and snail bait includes 3,5-dimethyl-4-methylthio-phenyl methylcarbamate, fine cereal flour, modified starch, a formaldehyde-releasing substance, and molasses.
This invention, accordingly, provides novel slug and snail baits, comprising
a) 3,5-dimethyl-4-methylthio-phenyl methylcarbamate of the formula, 
xe2x80x83optionally in a mixture with one or more other molluscicidally active compounds,
b) fine cereal flour,
c) modified starch and a formaldehyde-releasing substance,
d) molasses and
e) optionally additives.
Furthermore, it has been found that the novel slug and snail baits can be obtained when
(1) 3,5-dimethyl-4-methylthio-phenyl methylcarbamate of the formula, 
xe2x80x83optionally in a mixture with one or more other molluscicidally active compounds,
xe2x80x83and optionally in a mixture with additives, is mixed and finely ground,
(2) the resulting premix is mixed with
fine cereal flour,
modified starch and a formaldehyde-releasing substance and then sprayed with molasses,
(3) the resulting homogeneous mixture is admixed with sufficient water to form a dough,
(4) the dough is extruded and comminuted and
(5) the resulting product is dried.
Finally, it has been found that the novel slug and snail baits are highly suitable for controlling terrestrial slugs and snails.
It is extremely surprising that the slug and snail baits according to the invention have a better stability than the prior-art shaped articles for the same intended use. It is particularly unexpected that the baits according to the invention, in spite of containing a relatively small amount of adhesive, are, in particular with respect to rain water, considerably more stable than corresponding baits prepared by dry pressing which contain a considerably higher quantity of adhesive.
The slug and snail baits according to the invention have a number of advantages. Thus, they have high abrasion resistance. It is furthermore favourable that they maintain their shape and activity even after prolonged watering.
The slug and snail baits according to the invention are characterized by the constituents listed under (a) to (e).
The molluscicidally active compound that is contained in the baits according to the invention is in each case 3,5-dimethyl-4-methylthio-phenyl methylcarbamate of the formula (I), which is known under the common name methiocarb.
Other molluscidically active compounds which may additionally be present are preferably metaldehyde and metal chelates, such as complexes of ethylenediamine-tetraacetic acid and iron or copper ions.
The cereal flours that may be contained in the slug and snail baits according to the invention are commercial flours, such as wheat flour, rye flour, rice starch, inter alia. Preference is given to durum wheat flour and wheat flour. The flour is present in a fine form, preferably in particle sizes below 250xcexc.
In the present case, modified starch is to be understood as meaning commercial products of this type. Preference is given to cold-swelling maize starch.
As formaldehyde-releasing substances, the baits may comprise all customary products which are suitable for releasing formaldehyde. Preference is given to urea/formaldehyde condensates.
In the present case, molasses are to be understood as customary syrup-like mother liquors obtained in the manufacture of sugar.
Suitable additives which may be contained in the baits according to the invention are preferably preservatives, colorants, slug and snail attractants, grinding auxiliaries, bitter substances, homeotherm repellents and anticaking agents, and also water.
Examples of preservatives which may be mentioned are 2-hydroxybiphenyl, sorbic acid, p-hydroxy-benzaldehyde, methyl p-hydroxy-benzoate, benzaldehyde, benzoic acid, propyl p-hydroxy-benzoate and p-nitro phenol.
Examples of colorants which may be mentioned are inorganic pigments, iron oxide, titanium dioxide and Prussian Blue, and also organic dyes, such as anthraquinone, azo and metal phthalocyanine dyes.
Suitable slug and snail attractants are all customary substances suitable for this purpose. Examples which may be mentioned are plant extracts and derivatives thereof, and products of animal origin.
Suitable grinding auxiliaries are all substances which can customarily be used for this purpose. Kaolins, aluminas, talc, chalk, quartz powder and finely divided silica may be mentioned as being preferred.
Suitable homeotherm repellents which have a repellent effect on warm-blooded organisms, such as dogs or hedgehogs, are all components which are customary for this purpose. The example which may be mentioned is nonyloic acid vanillamide.
Suitable bitter substances are all substances which are customary for this purpose. An example which may be mentioned is denatonium benzoate.
Suitable anticaking agents are all substances which are customary for this purpose and which prevent lumping and caking. Examples which may be mentioned are moisture-adsorbing powders of kieselguhr, pyrogenic silica, tricalcium phosphate, calcium silicates, aluminium oxide, magnesium oxide, magnesium carbonate, zinc oxide, stearates and fatty amines.
The content of the individual components in the slug and snail baits according to the invention can be varied within a certain range. Thus, the concentrations
of active compound of the formula (I), optionally in a mixture with one or more other molluscicidally active compounds, are generally between 0.5 and 15% by weight, preferably between 1.0 and 13% by weight,
of cereal flour are generally between 60 and 90% by weight, preferably between 65 and 85% by weight,
of modified starch and formaldehyde-releasing substance are generally between 0.1 and 6% by weight, preferably between 0.2 and 5% by weight,
of molasses are generally between 1 and 10% by weight, preferably between 2 and 4% by weight, and
of additives are generally between 0 and 5% by weight, preferably between 0 and 3% by weight.
When carrying out the process according to the invention, preference is given to using those components which have already been mentioned as being preferred in connection with the description of the slug and snail baits according to the invention for the constituents listed under (a) to (e).
The quantities of the individual components are chosen such that the substances are present in the slug and snail baits according to the invention in the weight ratios mentioned above. However, the amount of water is such that a dough is formed in Step (3) of the process. In general, the amount of water used is between 25 and 35% by weight, preferably between 27 and 34% by weight, based on the other constituents. However, in the slug and snail baits according to the invention, the water content is considerably lower, since the product, which is initially obtained in moist form, is then dried in Step (5) of the preparation process. What remains is virtually only the residual moisture present in the cereal flour.
When carrying out the process according to the invention, the temperatures can be varied within a certain range.
Step (1) is generally carried out at temperatures between 0xc2x0 C. and 30xc2x0 C., preferably at room temperature,
Step (2) is generally carried out at temperatures between 0xc2x0 C. and 30xc2x0 C., preferably at room temperature,
Step (3) is generally carried out at temperatures between 0xc2x0 C. and 40xc2x0 C, preferably between 10xc2x0 C. and 30xc2x0 C.,
Step (4) is generally carried out at temperatures between 20xc2x0 C. and 60xc2x0 C., preferably between 30xc2x0 C. and 50xc2x0 C. and
Step (5) is generally carried out at temperatures between 20xc2x0 C. and 90xc2x0 C., preferably between 30xc2x0 C. and 80xc2x0 C.
Steps (1) to (3) and (5) of the process according to the invention are generally carried out under atmospheric pressure. However, it is also possible to carry out the drying process in Step (5) under reduced pressure. Step (4) is generally carried out under elevated pressure, preferably under a pressure between 30 and 100 bar.
All equipment which is customarily used for such processes can be employed for carrying out the process according to the invention. Thus, for comminuting the material in Step (1), customary grinding equipment, such as, for example, airjet mills, are used.
Suitable mixers for the mixing processes in Steps (2) and (3) are customary mixers into which additional substances, such as molasses and water, can be injected during the mixing process. Preference is given to using ploughshare mixers, paddle mixers and twin-screw extruders.
Suitable for the extrusion in Step (4) is the equipment which is customary in the food industry and which can be used to extrude a dough through perforated discs and then to comminute the extrudate.
Suitable for drying the moist product in Step (5) are customary apparatuses which are suitable for removing moisture from particulate solid substances. In a preferred embodiment, the moist product is initially predried in a fluidized bed and then dried to the desired final moisture in a separate piece of equipment.
Specifically, the process according to the invention is carried out by
mixing, in Step (1), the active compound of the formula (I), optionally in a mixture with one or more other molluscicidally active compounds and optionally with additives, such as, for example, grinding auxiliaries, preservatives, colorants, and the like, and finely grinding the resulting mixture,
mixing, in Step (2), the resulting premix with fine cereal flour, modified starch and formaldehyde-releasing substance, then adding molasses in liquid form and mixing the components to a homogeneous product,
adding, in Step (3), a sufficient quantity of water with mixing and kneading, so that a dough is formed,
extruding under pressure and comminuting, in Step (4), the dough and initially predrying and then drying, in Step (5), the particulate material, followed by cooling to room temperature.
When carrying out the process according to the invention, the size of the slug and snail baits can be varied within a certain range in the particular desired manner. In general, the dough is comminuted such that pellets or strand-shaped particles are formed. The average diameter or the average length of the particles is generally between 1 and 4 mm, preferably between 1.5 and 3 mm.
The slug and snail baits according to the invention are highly suitable for controlling terrestrial slugs and snails in agriculture and horticulture. The slugs and snails include all terrestrial slugs and snails, most of which occur as polyphagous pests in agricultural and horticultural crops. Important pests of these types are slugs, such as Arion rufus (red slug), Arion ater and other Arionidae, Limax species, furthermore field slugs, such as Deroceras reticulatum and Deroceras agreste from the family Limacidae, and species from the family Milacidae, and moreover harmful snails, such as those from the genera Cepaea, Discus, Helicigona and Helicella.
In the control of slugs and snails, the application rate of the baits according to the invention can be varied within a wide range. In general, between 2 and 15 kg of slug and snail bait are used per hectare, preferably between 3 and 7 kg per hectare.
The slug and snail baits according to the invention can be applied by customary methods, such as, for example, by scattering and drilling.
The invention is illustrated by the examples below.